When does political protest become terrorism?

The legal limits of government proscription powers

The distinction between political protest and terrorism has become one of the most contentious questions in contemporary British public law. Political movements have long employed disruption, civil disobedience and, on occasion, damage to property to challenge government policy. The state’s responsibility to protect people from violence and intimidation operates alongside its duty to protect political participation. The constitutional difficulty arises when the methods of a protest organisation bring it within legislation designed to combat terrorism, exposing both the organisation and its supporters to consequences extending far beyond the prosecution of particular criminal acts.

This question lies at the centre of R (Ammori) v Secretary of State for the Home Department, which is being heard by the Supreme Court on 4–5 November 2026. The proceedings concern the government’s decision to proscribe Palestine Action under section 3 of the Terrorism Act 2000. Proscription took effect on 5 July 2025, following parliamentary approval of an order adding the organisation to Schedule 2 of the Act.

In February 2026, the Divisional Court held that the decision was unlawful, finding that the Home Secretary had misapplied her published policy and that proscription interfered disproportionately with freedoms protected by Articles 10 and 11 of the European Convention on Human Rights (ECHR). The Court of Appeal reversed that judgment in June 2026, concluding that the Home Secretary had acted lawfully and that the restrictions on expression and association were proportionate. The Supreme Court has granted permission to appeal on the Convention-rights question, while refusing permission on the separate policy ground. As at 4 November 2026, the appeal is being heard and Palestine Action remains proscribed.

The case raises a problem wider than the activities of one organisation. Section 1 of the Terrorism Act 2000 expressly includes serious damage to property within the statutory definition of terrorism. Consequently, conduct undertaken in pursuit of a political cause may satisfy that definition even where the immediate objective is the destruction of property rather than injury to people. Once an organisation is proscribed, moreover, criminal liability can extend to membership, recruitment, expressions of support and public displays associated with the organisation.

The central argument of this essay is that the breadth of the terrorism definition makes rigorous scrutiny of proscription especially important. Serious property damage may establish the statutory threshold while leaving substantial questions about the necessity of criminalising an organisation’s membership and peaceful support. The government must justify the additional protection achieved by extending criminal liability from harmful conduct to political association. In Ammori, the strongest objection to proscription concerns that extension: the severity and reach of the restrictions require a closer relationship between the anticipated harm and the people whose freedoms are curtailed. A convincing civil-liberties analysis must examine that relationship throughout the proportionality assessment.

1. The statutory definition of terrorism

Political purpose and prohibited conduct

The starting point is section 1 of the Terrorism Act 2000. Broadly, the definition requires the use or threat of action involving one of several specified forms of harm, where the conduct is designed to influence a government or international governmental organisation, or to intimidate the public or a section of it, and is undertaken to advance a political, religious, racial or ideological cause.

The specified conduct includes serious violence against a person, serious damage to property, endangerment of another person’s life, serious risks to public health or safety, and action designed seriously to interfere with or disrupt an electronic system. Under section 1(3), action within section 1(2) involving firearms or explosives can qualify without satisfying the separate requirement of influencing government or intimidating the public. The requirement of advancing a political, religious, racial or ideological cause continues to apply.

The inclusion of property damage has particular significance for protest movements. Demonstrations are frequently intended to influence government. A political objective, therefore, is an ordinary characteristic of democratic protest and also an express component of the statutory definition of terrorism. Where a protest escalates into sufficiently serious property damage, the distinction between civil disobedience and terrorism may turn upon the nature and seriousness of the conduct rather than upon the cause that motivated it.

A hypothetical example demonstrates the difficulty. Activists might damage equipment belonging to a company whose activities they oppose, seeking to persuade the government to withdraw a contract or change its export policy. The political objective would supply part of the statutory test. The extent of the damage, the surrounding circumstances and the remaining statutory requirements would determine whether the conduct crossed the legal threshold. Although the public might ordinarily describe such behaviour as vandalism or sabotage, Parliament has authorised its treatment as terrorism where the statutory conditions are satisfied.

This approach reflects a deliberate legislative choice. In R v Gul [2013] UKSC 64, the Supreme Court examined the reach of section 1 and accepted that Parliament had enacted an exceptionally broad definition. The case concerned material depicting attacks by insurgents on military targets overseas, raising questions about whether such conduct fell within the domestic definition of terrorism.

The Court applied the statutory language according to its ordinary meaning and rejected an interpretation that would substantially narrow its operation by reference to an assumed international consensus. Nevertheless, at [62], the Court drew attention to the concerns surrounding the breadth of the definition and indicated that legislative reconsideration would be welcome.

The significance of Gul extends beyond the particular facts. A broad definition places considerable practical responsibility upon those authorised to deploy the powers attached to it. At [35]–[40] and [62]–[63], the Supreme Court also identified the difficulties of relying upon prosecutorial discretion to control expansive legislation. Clear legal boundaries offer stronger protection than an expectation that officials will use their powers sparingly. That concern is especially acute where the same definition activates restrictions upon political organisation.

Is serious property damage an adequate threshold?

The phrase “serious damage to property” contains an important uncertainty: the Terrorism Act provides no comprehensive definition of seriousness for this purpose. Financial loss may be relevant, but the gravity of an incident can also depend upon its method, its consequences for public safety, its effect upon essential infrastructure and the possibility of injury to employees, emergency responders or bystanders.

Jonathan Hall KC, the Independent Reviewer of Terrorism Legislation, examined this problem in The Terrorism Acts in 2024, published in April 2026. Hall distinguished possible approaches to defining serious property damage, including financial thresholds, methods of attack, risks to human life and connections with national security. He also suggested that a distinction might be drawn between expressive property damage intended primarily to attract attention and direct action designed to disrupt or coerce its target.

This is a useful analytical distinction. Painting a political slogan on a structure, disabling a substantial manufacturing operation and sabotaging equipment essential to national defence may all involve damage to property, but their social consequences differ considerably. A principled legal framework must be capable of evaluating those differences.

Hall nevertheless defended retaining serious property damage within the terrorism definition. Attacks on electricity supplies, transport systems or other important infrastructure can exercise considerable coercive pressure upon a population without directly targeting individuals. Conduct of that character may threaten collective security and democratic government as effectively as some forms of violence against people.

A more restrictive position has been advanced by Ian Turner in his 2026 article, ‘Defining terrorism in the UK and the proscription of Palestine Action: a critical legal assessment’, published in The International Journal of Human Rights. Turner argues that property damage should fall within the terrorism definition only where accompanied by an intention to cause serious harm to people, or at least a danger to civilian life.

Turner’s approach would strengthen the conceptual distinction between terrorism and serious political criminality. It would also reduce the risk that counter-terrorism legislation could be applied to disruptive protest campaigns presenting little danger to human safety.

The infrastructure examples require careful separation. Disabling an electricity network in circumstances threatening hospitals or emergency services may already engage section 1(2)(c) or (d), concerning danger to life and serious risks to public safety. Serious interference with electronic systems is separately covered by section 1(2)(e). These examples support a strong response to grave collective dangers. Their force as a justification for treating substantial financial damage alone as terrorism is considerably weaker. Turner’s inclusion of danger to civilian life also accommodates risks arising without an intention to injure.

A more convincing approach to reform would narrow the property-damage limb around the character of the threatened harm. Financial cost is relevant to the gravity of a property offence; exceptional counter-terrorism powers require a more demanding justification concerning danger to people or comparably grave threats to collective security. Where economic coercion alone is relied upon, Parliament should define the exceptional scale and consequences required. An open-ended reference to national security would leave much of the present uncertainty intact.

The present statutory definition remains broad. The case for reform follows from the consequences attached to it: the greater the range of political conduct captured at the threshold, the more important the legal safeguards governing the use of counter-terrorism powers become.

Property damage, rescue and conscientious intervention

The moral significance of damage depends upon what an intervention protects as well as what it destroys. Breaking a lock to free a trafficked person and forcing open an enclosure to rescue an animal can both express a claim that preventing suffering outweighs an owner’s control. An anti-speciesist analysis evaluates that claim by reference to sentience, suffering and the consequences of intervention. It challenges the assumption that describing an act as damage to property settles its moral character.

In England and Wales, the Criminal Damage Act 1971 already gives legal effect to some protective interventions. Section 5(2)(a) recognises an honest belief in the actual or hypothetical consent of someone the defendant believed entitled to authorise the damage. In Attorney General’s Reference (No 1 of 2023) [2024] EWCA Crim 243, [45], the Court of Appeal illustrated this with a window broken to rescue a child from a hot car. Section 5(2)(b) separately concerns action to protect property, coupled with honest beliefs that protection is immediately required and that the means are reasonable. Section 10 includes captive animals within the definition of property, bringing their protection within the potential scope of this defence.

Section 3 of the Criminal Law Act 1967 authorises reasonable force to prevent crime. Its application to intervention against unlawful captivity or animal cruelty depends upon the relevant offence and the circumstances. In R v Jones (Margaret) [2006] UKHL 16, [72]–[85], Lord Hoffmann emphasised objective reasonableness, the immediacy of the danger and the availability of official protection. Lawfully licensed animal experimentation is governed by the Animals (Scientific Procedures) Act 1986, a regime recognised by section 58 of the Animal Welfare Act 2006. The ethical challenge to that regime concerns the standards that the law itself should adopt.

These defences address liability for particular offences; terrorism classification has its own statutory requirements. Their wider significance is methodological: purpose, urgency, threatened suffering and actual consequences deserve examination alongside financial loss. For proscription, even a justified prosecution of an individual leaves a further question about the suppression of peaceful association across an organisation’s support base. A property-centred account of the original incident provides an incomplete answer to that constitutional question.

The international context

International law provides an important comparison, although it has yet to produce a single universally binding definition of terrorism.

United Nations Security Council Resolution 1566 (2004), paragraph 3, refers principally to grave criminal acts involving an intention to cause death or serious bodily injury, or the taking of hostages, for purposes including intimidation or coercion. That formulation gives greater prominence to violence against people than the domestic definition in the Terrorism Act 2000.

United Nations human rights experts have criticised the use of terrorism legislation against political protest involving property damage, arguing for a closer relationship between terrorist classification and serious harm to individuals. Their concerns illuminate the civil-liberties risks of an expansive definition.

For domestic courts, Parliament’s statutory test remains the operative standard. As Gul explains, the international materials offer insufficient agreement to justify replacing that test through interpretation alone. Their principal contribution is to demonstrate the policy choices involved in defining terrorism and the scope for a more tightly drawn legislative response.

2. Proscription: from punishment of conduct to restriction of association

The Home Secretary’s statutory power

Section 3(4) of the Terrorism Act 2000 permits the Home Secretary to proscribe an organisation where she believes it is concerned in terrorism. Under section 3(5), an organisation may satisfy that description by committing or participating in terrorist acts, preparing for terrorism, promoting or encouraging terrorism, or otherwise being concerned in terrorism.

The language establishes a threshold for the exercise of discretion. Once that threshold is met, the Home Secretary must determine whether proscription is justified.

The government’s published policy identifies relevant considerations, including the nature and scale of an organisation’s activities, the threat it poses to the United Kingdom, threats to British nationals overseas, its presence within the United Kingdom and the implications for international counter-terrorism cooperation. The Home Office’s policy statement of 26 October 2026 restates these factors and expressly recognises the duty to exercise the discretion compatibly with Convention rights.

The order-making process also involves parliamentary scrutiny. Subject to the statutory urgency procedure, a proscription order requires approval by both Houses of Parliament under section 123. That approval provides democratic authority for an unusually intrusive measure, while judicial review supplies legal scrutiny of the executive decision and its compatibility with Convention rights.

The two forms of accountability address different constitutional concerns. Parliament determines whether the proposed designation should receive legislative approval. The courts examine whether the statutory power has been exercised lawfully, including whether its effects upon protected rights satisfy the requirements of the Human Rights Act 1998.

The consequences of listing an organisation

The practical effects of proscription explain why the proportionality inquiry is so important.

Sections 11–13 of the Terrorism Act 2000 create offences connected with belonging to a proscribed organisation, inviting support, organising certain meetings, expressing supportive opinions with the requisite recklessness, and displaying clothing or articles in circumstances giving rise to reasonable suspicion of membership or support. Further offences concern the provision and handling of money and property connected with terrorism.

The maximum sentence on indictment for offences under sections 11 and 12 is 14 years’ imprisonment. Section 13 creates a separate, summary offence. Proscription therefore changes the legal position of people whose conduct may consist of association or communication rather than participation in destructive acts.

An ordinary criminal prosecution addresses an identified offence and the responsibility of the individual accused. Proscription operates prospectively against an organisation and creates a framework of criminal liability surrounding its continued existence. Its intended preventive effect includes hindering recruitment, fundraising, communications and organisational coordination.

The Divisional Court recognised the depth of this intervention in Ammori [2026] EWHC 292 (Admin), observing at [135] that proscription is intended to bring about the cessation of an organisation’s existence.

The result is a substantial enlargement of the relevant constitutional interests. The assessment must consider the interests of those affected by the organisation’s harmful activities alongside the rights of members, lawful supporters and people wishing to express political views associated with its objectives.

Criminalising support and the chilling effect

The Supreme Court’s judgment in R v ABJ; R v BDN [2026] UKSC 8 provides important guidance on the interpretation of section 12(1A).

Lord Reed explained that the offence requires knowingly supportive expression and recklessness about encouraging another person’s support. Recklessness requires both awareness of an actual risk and objectively unreasonable risk-taking in the circumstances known to the defendant: [70]–[82]. At [60]–[61], the Court distinguished support for an organisation from agreement with its political objectives.

This interpretation preserves space for political debate. Advocacy for Palestinian rights and criticism of British or Israeli government policy fall within that protected sphere. The distinction helps explain why the wider chilling effect matters: uncertainty about organisational support can deter participation in an otherwise lawful cause.

ABJ treats conviction as in principle proportionate once the offence’s ingredients are established, with safeguards through robust judicial scrutiny of evidential sufficiency and proportionate sentencing: [129]–[138]. The justification for designating the organisation therefore assumes particular importance: it establishes the status upon which this criminal liability depends.

Yet the practical operation of proscription presents an additional problem. Individuals may be uncertain how the law applies to political statements, particularly where the boundary between endorsing a cause, supporting an organisation and objecting to its proscription becomes controversial.

The separate display offence raises a sharper problem. In Pwr v DPP; Akdogan and another v DPP [2022] UKSC 2, the Supreme Court held that section 13(1) imposes strict liability, subject to knowledge of the act of wearing, carrying or displaying the article. It upheld the provision’s compatibility with Article 10. Liability turns on the circumstances arousing reasonable suspicion of membership or support, rather than an intention to communicate support: [26] and [68]–[74].

The Independent Reviewer has examined the resulting uncertainty about placards opposing proscription itself. His analysis at [3.37]–[3.43] stresses that section 13 concerns reasonable suspicion about the person’s membership or support. The constitutional concern is substantial: a power restricting political association also creates uncertainty about how citizens can publicly challenge the restriction.

The consequences are evident in official enforcement data. Home Office statistics for the year ending 31 March 2026 record 2,819 terrorism-related arrests linked to suspected support for Palestine Action following its proscription. Of those arrests, 484 had resulted in charges as at 5 May 2026, while 2,287 cases remained subject to bail or release under investigation.

These figures measure enforcement activity and should be assessed alongside the eventual outcomes of proceedings. Their immediate constitutional significance lies in the scale of exposure to arrest, investigation and potential punishment. The burden on political participation begins when the criminal process is engaged, often well before any determination of guilt. The designation’s proportionality therefore requires attention to its operation across the support base as well as its effect on those planning harmful acts.

A legal regime affecting political speech must be evaluated both by its formal requirements and by its foreseeable influence upon lawful participation. At [153] of Ammori, the Court of Appeal accepted a significant chilling effect on lawful supporters of the Palestinian cause. That recognition gives the concern an evidential foundation within the litigation itself. The broader democratic cost includes people choosing silence or withdrawal because they fear the consequences of being associated with a controversial movement.

3. Ammori: why the courts disagreed

The factual and administrative background

Palestine Action emerged as a direct-action movement opposing businesses connected with the supply of military equipment to Israel. Its activities included demonstrations, occupations, disruption and deliberate damage to property.

The government’s assessment of the organisation developed before the June 2025 incident at RAF Brize Norton, where activists entered a military airfield and damaged RAF aircraft.

In March 2025, the Joint Terrorism Analysis Centre (JTAC) assessed that Palestine Action met the statutory criteria for being concerned in terrorism. The assessment identified three incidents involving serious damage to property: an incident at Thales premises in Glasgow in 2022, an incident at Instro Precision in Kent in June 2024, and an incident at Elbit Systems premises in Bristol in August 2024.

The Court of Appeal’s judgment records the government’s broader concerns about the organisation’s operational methods, including covert activity, coordinated planning, an internal manual and an apparent escalation in the seriousness of its actions. Its assessment also referred to risks faced by staff and police officers and to the targeting of businesses connected with defence and national infrastructure.

The Home Secretary confirmed her decision to proscribe the organisation on 20 June 2025, following the Brize Norton incident. The order subsequently received parliamentary approval and took effect on 5 July 2025.

These matters form the evidential foundation for the government’s position. The legal argument advanced in the proceedings concerned the relationship between the seriousness of that foundation and the consequences of proscription.

The Divisional Court: the consequences outweighed the justification

In R (Ammori) v Secretary of State for the Home Department [2026] EWHC 292 (Admin), the Divisional Court accepted that Palestine Action had undertaken activities amounting to terrorism under section 1 of the 2000 Act.

The Court also rejected the characterisation of the organisation as an ordinary, entirely peaceful protest movement. Its judgment recognised significant criminal conduct, the seriousness of certain attacks and the government’s responsibility to prevent further harm.

Nevertheless, it held that proscription was disproportionate.

At [138]–[140], the Court attached particular importance to the limited number of incidents classified as terrorism in the context of the organisation’s wider activities. It considered the interference with freedoms of expression and association exceptionally substantial, while recognising that the criminal law remained available to prosecute individuals responsible for damaging or violent conduct.

The Court’s reasoning is best understood as a judgment about the justification for escalating from ordinary criminal enforcement to a comprehensive organisational ban.

It also acknowledged the difficulties surrounding alternatives. At [132]–[134], the Divisional Court rejected the suggestion that affected businesses could simply be left to obtain civil injunctions. It recognised the limitations, expense and potential overbreadth of private litigation against organised criminal activity.

The Divisional Court therefore reached its conclusion after accepting both the seriousness of the threat and the shortcomings of some less intrusive measures. Its ultimate assessment was that the nature, scale and persistence of the terrorist activities did not justify the full consequences of proscription.

The Court of Appeal: organisational risk and preventive disruption

The five-judge Court of Appeal reached the opposite conclusion in Secretary of State for the Home Department v Ammori [2026] EWCA Civ 721.

Its analysis placed greater weight upon the organisation’s activities as a whole, the prospect of further serious incidents and the practical benefits of disrupting the organisation before further attacks occurred.

At [89], the Court of Appeal held that the Home Secretary was entitled to consider both terrorist and other activities in assessing the future risk posed by the organisation. This approach treated the three identified terrorist incidents as part of a larger pattern of conduct, rather than as isolated events whose significance could be measured principally by their number.

The Court also accepted the police assessment that prosecutions for individual offences did not adequately address the organisation’s operational capacity. Preventing future attacks might require intervention against recruitment, funding, planning and the network through which offences were organised.

Under the proportionality analysis, the Court of Appeal gave considerable weight to the Home Secretary’s responsibility for national security and her access to specialist assessments. It nevertheless recognised the important rights affected by the decision, including the interests of lawful supporters and the wider chilling effect upon political expression.

At [180], the Court acknowledged that the decision might have been “borderline”, while concluding that the Home Secretary was entitled to the appropriate degree of latitude in making it.

The Court of Appeal’s approach demonstrates the preventive logic of proscription. Its central concern was the anticipated development of the organisation’s activities and the state’s ability to reduce the risk of further harm. The Divisional Court placed greater weight upon the demonstrated scale of terrorist activity and the severity of the resulting restrictions. Their disagreement exposes a constitutional choice about how much uncertainty in a prediction of future harm can justify an extensive, present restriction of political association.

The different conclusions emerged from the weight assigned to competing considerations within the proportionality exercise. The Supreme Court is now considering the constitutional and Convention-law limits of that exercise.

4. Freedom of expression and association under the ECHR

Political expression and peaceful assembly

Article 10 protects freedom of expression, including political speech, criticism of government and communication of controversial ideas. Article 11 protects freedom of peaceful assembly and association.

Both rights are central to democratic participation. Political movements allow individuals to organise collectively, challenge powerful institutions and communicate grievances that may otherwise receive limited public attention.

The rights are qualified. Articles 10(2) and 11(2) permit restrictions prescribed by law and necessary in a democratic society for specified legitimate aims, including national security, public safety, prevention of crime and protection of the rights of others.

Proscription engages those legitimate aims directly. The state must be able to protect employees, businesses, emergency responders and the wider public from serious politically motivated harm. The difficult question is whether the particular restriction imposed is proportionate to that objective.

European human-rights jurisprudence offers a principled distinction between protected peaceful protest and conduct justifying stronger state intervention.

In Ezelin v France (1991) 14 EHRR 362, the European Court of Human Rights emphasised the importance of protecting an individual’s participation in a demonstration where the individual had not personally engaged in reprehensible conduct.

In Kudrevičius and Others v Lithuania (2015), application no 37553/05, the Grand Chamber recognised that peaceful assemblies can cause substantial disruption, while accepting that deliberate obstruction and serious interference with the rights of others may justify proportionate sanctions.

The Supreme Court’s decision in DPP v Ziegler [2021] UKSC 23 likewise illustrates that the Convention rights engaged by peaceful, obstructive protest can require close consideration in an individual criminal prosecution.

For criminal damage, Attorney General’s Reference (No 1 of 2022) [2022] EWCA Crim 1259, [115]–[121], recognises limited scope for an individual Convention proportionality defence where damage is minor or trivial. It treats prosecution and conviction for significant damage as proportionate even where the conduct is peaceful. That capacity to punish substantial damage through ordinary criminal proceedings strengthens the demand for a separate explanation of why peaceful association must also be curtailed.

These authorities preserve a meaningful distinction between the rights of peaceful participants and the legal consequences of harmful conduct. They also show that proportionality depends upon context: the nature of the protest, the seriousness of the interference, the conduct of those involved and the interests of third parties.

Association and the significance of collective responsibility

The right of association introduces an additional dimension to proscription disputes.

Political organisations depend upon membership, communications, finance and the ability to recruit supporters. In Sidiropoulos and Others v Greece (1998), application no 26695/95, [40], the European Court identified collective organisation as a central aspect of Article 11. An established association embodies relationships, experience, resources and an accumulated public identity. Suppressing that capacity imposes a democratic loss extending beyond the restriction of individual statements.

The state’s concern, however, may arise precisely because harmful acts are planned, financed or encouraged through an organisation. An assessment confined to the culpability of individual participants could overlook the collective structure that enables repeated offending.

European human-rights law recognises that organisations may be dissolved where their conduct presents a sufficiently serious threat to democratic society and the rights of others.

In Herri Batasuna and Batasuna v Spain (2009), applications nos 25803/04 and 25817/04, the European Court of Human Rights upheld the dissolution of political parties whose activities and connections formed part of a strategy associated with ETA terrorism.

Similarly, Vona v Hungary (2013), application no 35943/10, concerned the dissolution of an association linked to intimidating paramilitary activity directed against Roma communities. The Court accepted that preventive action against an organisation may be justified where its activities create a sufficiently serious threat to the rights of others.

The threat in those cases arose from connections with terrorist violence or organised intimidation directed against a vulnerable community. Their preventive reasoning is important, while its application to a protest movement requires careful attention to the nature and gravity of the particular threat. The relevant comparison concerns the evidence supporting dissolution and its consequences for democratic participation. Treating every organisation falling within a broad domestic terrorism definition as presenting the same constitutional problem would bypass that examination.

Applied to protest movements, the critical inquiry concerns organisational responsibility. Evidence of leadership involvement, planning, encouragement, endorsement, financial support or repeated coordinated conduct may justify treating an incident as representative of an organisation’s activities. The mere fact that an individual once associated with a movement has committed an offence provides a much weaker basis for imposing consequences upon every supporter.

A careful assessment of organisational attribution is therefore essential to maintaining the distinction between collective responsibility and guilt by association.

The limits of Article 17

The government argued in the Court of Appeal that Article 17 ECHR, which prevents Convention rights being invoked for purposes destructive of those rights, excluded the relevant claims from Articles 10 and 11.

The Court of Appeal rejected that argument at [91]–[97].

The judgment recognised that the rights affected included those of individuals whose own conduct remained peaceful and lawful. Their participation in political debate and assembly could be adversely affected by the designation, regardless of the organisation’s involvement in serious criminal acts. The restrictions consequently required justification under Articles 10 and 11.

This aspect of the judgment is constitutionally significant. It establishes the need to examine the effect of proscription upon people beyond those responsible for the conduct prompting the government’s decision.

The proportionality inquiry must therefore address the wider consequences for democratic participation, even where the state possesses compelling evidence of dangerous organisational activity.

5. Proportionality: the decisive legal inquiry

The four-stage approach

The framework for assessing restrictions upon Convention rights was stated in Bank Mellat v HM Treasury (No 2) [2013] UKSC 39.

In broad terms, the court asks:

1. Whether the objective is sufficiently important to justify limiting a fundamental right.
2. Whether the measure is rationally connected to that objective.
3. Whether a less intrusive measure could achieve the objective without unacceptably compromising its achievement.
4. Whether the measure strikes a fair balance between the rights affected and the public interest pursued.

In Ammori, the government’s principal objectives were the protection of national security and the rights of others. These are expressly recognised legitimate aims under Articles 10(2) and 11(2).

The Court of Appeal accepted that proscription was rationally connected to those objectives because of its capacity to disrupt the organisation’s operations and reduce the risk of future harmful activity.

The more difficult questions arise at the third and fourth stages.

Less intrusive alternatives

The claimant argued that the government could rely upon prosecutions, civil injunctions and other measures directed at those involved in criminal acts.

This argument rests upon a familiar constitutional principle: restrictions upon fundamental freedoms should extend no further than necessary to achieve their legitimate objective.

The government’s answer concerned the organisational character of the threat. Proscription supplies additional offences and investigatory opportunities directed at recruitment, financing and operational capacity. Its preventive rationale has genuine force where a network enables repeated serious attacks.

Ordinary criminal enforcement also has a preventive dimension. Conspiracy, attempts and offences of encouraging or assisting crime can address conduct before a completed attack. The Court of Appeal recorded the claimant’s reliance on preparatory offences at [131], before accepting the operational advantages of proscription. A fair comparison must therefore examine the respective reach and effectiveness of both preventive frameworks.

The Court of Appeal accepted the government’s reasoning at [124]–[140], relying upon police assessments of the limitations of existing powers. It considered private injunctions, other targeted measures and the possibility of targeting a specific component of the organisation. The criticism concerns the standard used to assess these alternatives and the weight attached to their limitations.

The formulation of the objective is crucial. Protecting people and preventing serious attacks are public interests against which alternative measures can be compared. Dismantling an organisation is a means chosen to pursue those interests. If dismantling becomes the objective against which every alternative is judged, measures preserving lawful association will predictably appear inadequate. The reasoning at [129] and [133]–[139] warrants scrutiny on precisely this ground.

A rigorous necessity assessment should compare how effectively available measures address the identified harm and explain the additional protection supplied by proscription. It should examine the anticipated seriousness and likelihood of further incidents, organisational responsibility for them, and the practical limitations of more targeted powers. The assessment can be prospective: evidence may justify rejecting an alternative before it has been tried. What matters is a substantiated comparison of protection and interference.

The Court of Appeal also identified the advantage of offences that are easier to prove, at [133]. That advantage carries a corresponding constitutional cost when the conduct made easier to prosecute consists of membership, expression or association. The government gains preventive reach by criminalising a wider range of activity. The persuasive weight of that gain depends upon the connection between the additional restrictions and the prevention of serious harm.

The final balance

The fourth stage requires an overall judgment about the relationship between the measure’s benefits and its consequences for protected rights.

Several matters support proscription where a protest organisation has engaged in serious damage to property. These include escalating methods, risks of injury, threats to essential infrastructure, coordinated criminal activity and evidence that the organisation intends to continue or intensify its campaign. The rights of employees and other people exposed to such conduct deserve substantial weight.

The countervailing considerations concern the breadth of the restrictions imposed upon association and expression. Proscription reaches peaceful participants and criminalises forms of membership and support that were previously lawful. It can also deter participation in the wider cause. These effects concern the conditions of democratic engagement: the ability to organise, communicate collectively, challenge government policy and sustain political opposition.

The Court of Appeal recognised both the chilling effect upon supporters of the wider cause and the rights of people supporting the organisation itself: [153]–[154]. At [173], however, it attached weight to the continuing freedom to express support for Palestine and opposition to Israeli policy, describing the rights’ core as effectively preserved.

That reasoning gives insufficient weight to Article 11’s independent protection of association. The opportunity to advocate the same cause elsewhere preserves a freedom to express ideas, but an organisation also provides a particular set of relationships, resources and collective opportunities. Its suppression demands justification by reference to that loss. The Court’s recognition of organisational supporters’ rights at [154] sits uneasily with the reduced significance accorded to their chosen association at [173].

On this point, the Divisional Court’s approach offers the more convincing constitutional analysis. It treated the breadth of the organisational restriction as a substantial cost requiring commensurate justification, even after accepting serious wrongdoing and the risk of repetition. The central issue is the additional security benefit obtained by suppressing peaceful membership and support. A demanding fair-balance assessment should require that benefit to justify the loss of collective political capacity and the foreseeable effects on wider participation.

6. Judicial scrutiny and executive responsibility for national security

A significant aspect of the Supreme Court appeal concerns the relationship between judicial scrutiny and ministerial responsibility.

The Home Secretary has access to intelligence assessments, specialist policing advice and information concerning potential future threats. Courts recognise the practical and constitutional importance of that expertise.

In Shvidler v Secretary of State for Foreign, Commonwealth and Development Affairs [2025] UKSC 30, the Supreme Court examined the approach to proportionality in challenges to executive sanctions. The majority emphasised that courts should respect the constitutional responsibilities and institutional competence of the executive when evaluating matters within its particular expertise.

The Court of Appeal applied that approach in Ammori. At [104]–[116], it reasoned that the Home Secretary deserved substantial latitude when assessing future threats to national security and the public interest in preventing them.

The scope of that latitude deserves close scrutiny. At [107], the Court of Appeal itself distinguished the Home Secretary’s expertise in national security from the assessment of the decision’s impact on those affected. That distinction should carry substantial weight in the final balance.

Ministerial expertise is especially valuable when identifying patterns of activity, assessing intelligence and estimating the likelihood of further incidents. Judicial competence is especially important when evaluating the nature and extent of an interference with fundamental rights and determining whether the evidence justifies that interference.

This division of responsibility provides a principled basis for intensive review. Intelligence expertise can establish an organisation’s capability, intentions and likely future conduct. The court must then determine how those findings justify the breadth and severity of the legal restriction. Where the terrorism definition already extends to property damage, the statutory label supplies particularly little assistance in deciding how much political freedom should be sacrificed. The concrete threat and the actual interference must do the analytical work.

A further difficulty arises where the courts assess evidence unavailable for public inspection. The Ammori litigation has involved both open and closed material, together with the participation of special advocates. Such procedures can assist the court in examining sensitive intelligence while preserving confidentiality.

Closed procedures also increase the importance of clear public reasoning. Commentary based on the open judgments necessarily has a more limited evidential foundation than the courts’ assessment. Within that constraint, the public reasons should explain the nature of the threat, the limitations of targeted measures and the relationship between the predicted harm and the restriction imposed. The constitutional legitimacy of suppressing an organisation depends partly upon the quality of that explanation.

Judicial supervision remains central to the constitutional arrangement established by the Human Rights Act 1998. Section 6 requires public authorities to act compatibly with Convention rights, subject to the Act’s statutory qualifications. Determining compatibility in a contested case is ultimately a legal responsibility.

7. Implications for other protest movements

The implications of Ammori extend to environmental, animal-rights, anti-war and other movements that use disruptive direct action.

The statutory definition applies across political and ideological causes. Accordingly, an organisation engaged in sufficiently serious property damage may fall within section 1 where the remaining conditions are satisfied. The possibility is particularly significant when a campaign targets infrastructure, industrial premises, transport facilities or equipment used by public authorities.

Yet the effect of Ammori will depend largely upon the guidance the Supreme Court provides on the separate discretion to proscribe.

If the Court endorses a broad approach to preventive organisational disruption, the Home Secretary may enjoy substantial latitude where intelligence suggests that serious unlawful activity will continue or escalate. The risk for other movements is that organisational scale, fundraising and effective coordination could be treated principally as capacities to be disrupted, even where they also sustain extensive lawful campaigning.

A more demanding approach to proportionality would require careful differentiation between an organisation’s capacity for serious harmful conduct and its capacity for lawful political participation. Evidence linking leadership and operational structures to the predicted threat would remain central. So would the feasibility of targeted intervention and the rights of peaceful participants. Such an approach would better protect movements whose criticism of government or powerful commercial interests makes their collective activity politically contentious.

Either approach would operate within the statutory definition enacted by Parliament. Legislative reform would remain the principal means of narrowing the property-damage limb itself.

The need for principled distinctions

The danger of an expansive statutory definition lies partly in the variety of conduct it encompasses.

A protest organisation responsible for occasional but serious criminal damage presents a different factual picture from one systematically sabotaging essential infrastructure or coordinating attacks that place workers at substantial risk. These differences should influence the assessment of prospective harm and the necessity of organisational proscription.

The legal framework would benefit from an express requirement to consider:

• The seriousness, frequency and expected continuation of conduct meeting the terrorism definition.
• The degree of organisational planning, direction or endorsement.
• The risk to human safety, essential infrastructure and the rights of third parties.
• The likely preventive effectiveness of proscription when compared with targeted criminal and civil powers.
• The consequences for peaceful members, supporters and wider political participation.
• The continuing justification for maintaining the designation as circumstances change.

Such considerations would support consistent decision-making across politically diverse movements. They would also help ensure that the exceptional consequences of proscription are justified by the nature of the threat rather than the unpopularity of a political cause.

Continuing review and the durability of proscription

A further concern is the duration of a proscription order.

Sections 4 and 5 of the Terrorism Act provide a mechanism for an organisation or a person affected by proscription to seek deproscription, followed by an appeal to the Proscribed Organisations Appeal Commission if the application is refused. The Home Office’s October 2026 policy statement confirms that the list is kept under review, that the minister can initiate deproscription and that applications must be determined within 90 days: [17] and [20]–[25]. Proscription orders nevertheless ordinarily continue without a fixed expiry date.

The House of Commons Library has noted repeated recommendations by Independent Reviewers of Terrorism Legislation for time limits or periodic review. Such safeguards would require renewed attention to the evidence supporting a designation and to the continuing necessity of restrictions upon association and expression.

Where proscription is justified by a prediction of future harm, its continuing legitimacy should respond to changes in the organisation, its activities and the threat it presents. An order supported by compelling evidence at the time of designation may require reconsideration if the factual circumstances materially change.

A fixed renewal requirement would place the responsibility for demonstrating continuing necessity upon the state. The statutory application route places the burden of initiating a challenge upon people already operating under the restrictions they seek to remove. Periodic, reasoned renewal would better align the duration of the designation with the evidence of continuing harm and give practical effect to the requirement of proportionality.

Conclusion

The Terrorism Act 2000 gives the government power to proscribe an organisation involved in sufficiently serious politically motivated property damage. The breadth of that jurisdiction makes the justification for its exercise decisive. Proscription transforms the legal position of members and supporters, extending criminal liability into activities through which people ordinarily participate in political life.

The strongest case against the proscription of Palestine Action concerns that transformation. Both courts accepted serious harmful conduct and the need for effective prevention. The more persuasive element of the Divisional Court’s reasoning was its insistence upon a proportionate relationship between the evidenced threat and the exceptionally broad interference with political association. The Court of Appeal’s emphasis on organisational disruption and executive expertise gives too little weight to the independent democratic value of the association being suppressed.

A rights-protective approach would require a convincing explanation of the additional security benefit achieved by criminalising peaceful membership and support, measured against realistically available alternatives. It would also give full weight to the recognised chilling effect on lawful pro-Palestinian participation. Preserving the ability to express a general political opinion addresses only part of the loss when the state dismantles the collective structures through which that opinion is pursued.

The purpose and consequences of direct action deserve the same careful differentiation. Ordinary criminal law can evaluate personal responsibility, lawful excuse and proportionate punishment. Organisational proscription adds a further layer of coercion whose justification must account for those people drawn within its reach through association alone. That is the constitutional step demanding the closest scrutiny in Ammori.

The Supreme Court’s pending decision will shape the practical boundary between the control of harmful conduct and the suppression of political organisation. The stronger constitutional principle is that the state must demonstrate why exceptional restrictions upon collective political freedom are necessary to meet the particular threat. The breadth of the statutory definition makes that requirement more important.

References

Cases

Attorney General’s Reference (No 1 of 2022) [2022] EWCA Crim 1259, [2023] KB 37.

Attorney General’s Reference (No 1 of 2023) [2024] EWCA Crim 243, particularly [40]–[50].

Bank Mellat v HM Treasury (No 2) [2013] UKSC 39, [2014] AC 700.

Director of Public Prosecutions v Ziegler [2021] UKSC 23.

Ezelin v France (1991) 14 EHRR 362.

Herri Batasuna and Batasuna v Spain (2009) applications nos 25803/04 and 25817/04.

Kudrevičius and Others v Lithuania (2015) application no 37553/05 (Grand Chamber).

Pwr v Director of Public Prosecutions; Akdogan and another v Director of Public Prosecutions [2022] UKSC 2, [2022] 1 WLR 789, particularly [26] and [68]–[74].

R (Ammori) v Secretary of State for the Home Department [2026] EWHC 292 (Admin). Official judgment.

R v ABJ; R v BDN [2026] UKSC 8. Supreme Court judgment.

R v Gul [2013] UKSC 64, [2014] AC 1260. Supreme Court judgment.

R v Jones (Margaret) [2006] UKHL 16, [2007] 1 AC 136, particularly [72]–[85].

Secretary of State for the Home Department v Ammori [2026] EWCA Civ 721. Official judgment.

Sidiropoulos and Others v Greece (1998) application no 26695/95, particularly [40].

Shvidler v Secretary of State for Foreign, Commonwealth and Development Affairs [2025] UKSC 30. Supreme Court judgment.

Vona v Hungary (2013) application no 35943/10.

Legislation

Animal Welfare Act 2006, s 58.

Animals (Scientific Procedures) Act 1986.

Criminal Damage Act 1971, particularly ss 1, 5 and 10.

Criminal Law Act 1967, s 3.

Human Rights Act 1998, particularly s 6 and Sch 1, Arts 10 and 11.

Terrorism Act 2000, particularly ss 1, 3–5, 11–13, 15–18 and 123, and Sch 2.

Academic literature and official materials

Hall J, The Terrorism Acts in 2024: Report of the Independent Reviewer of Terrorism Legislation (2026), particularly paras 3.14–3.32 and 3.37–3.43. GOV.UK.

Home Office, Statement in relation to the Secretary of State’s powers under section 3 of the Terrorism Act 2000 (26 October 2026), particularly paras 7–8, 17 and 20–25. GOV.UK.

Home Office, Operation of police powers under the Terrorism Act 2000 and subsequent legislation: Arrests, outcomes, and stop and search, Great Britain, quarterly update to March 2026 (2026). GOV.UK.

House of Commons Library, Proscribed Terrorist Organisations (Research Briefing SN00815, 27 March 2026). Parliament.uk.

Supreme Court of the United Kingdom, R (on the application of Ammori) v Secretary of State for the Home Department, UKSC/2026/0099, case summary and appeal information. Supreme Court case page.

Turner I, ‘Defining terrorism in the UK and the proscription of Palestine Action: a critical legal assessment’ (2026) The International Journal of Human Rights, DOI: 10.1080/13642987.2026.2680567. Open-access full text.

Office of the United Nations High Commissioner for Human Rights, ‘UN experts urge United Kingdom not to misuse terrorism laws against protest’ (2025). OHCHR.

United Nations Security Council, Resolution 1566 (2004), UN Doc S/RES/1566(2004), para 3. United Nations Digital Library.

European Court of Human Rights, Guide on Article 11 of the European Convention on Human Rights: Freedom of assembly and association (updated 28 February 2026). Council of Europe.